#include <iostream>
#include <iomanip>

#include <algorithm>
#include <math.h>

#include <string>
#include <list>
/////////
#define REP(i, x, n) for(int i = x; i < n; i++)
#define rep(i,n) REP(i,0,n)
#define P(p) cout<<(p)<<endl;
/////////
typedef long long LL;
typedef long double LD;
/////////
using namespace::std;
/////////
int N;//[1,10^5]種類
LL C[(int)1e5];//[1,10^18]
LL D[(int)1e5];//[1,10^18]

int main(void){
	cin.tie(0);
	ios::sync_with_stdio(false);
	cout << fixed;//
	//cout << setprecision(6);//

	cin >> N;
	rep(i,N){
		cin>>C[i]>>D[i];
	}
	//////////////
	LL mod = (int)1e9 + 7;
	LL sum = 0;
	rep(i,N){
		sum += (((C[i]+1)/2)%mod) * (D[i]%mod);
		sum %= mod;
	}
	P(sum);
	return 0;
}